Composite containers are widely used commercially for packaging various products such as snack foods, refrigerated dough products, and the like. Typically, the containers are formed of a helically or convolutely wrapped paperboard or boardstock layer, an inner liner layer providing a moisture barrier function, and an exterior layer that usually forms a label for printed indicia and/or graphics. The various layers of the container are wrapped in strip form onto a mandrel and are secured together by an adhesive applied between the confronting faces of the adjacent layers.
Water-based or "wet" adhesives have become popular because of concerns that the use and disposal of solvent-based adhesives may cause harm to the environment. Conventionally, a wet adhesive is applied to substantially the entire surface of a strip. The water in the adhesive has a tendency to permeate the paperboard body wall and, as a result, the stiffness and dimensional stability of the tubular body wall are compromised.
Consequently, it has been necessary in many cases to hold completed cans in storage for a period of time prior to being filled with product and having end closures seamed on the cans, so that the cans have time to dry to increase their strength sufficiently to be able to tolerate the stresses imposed on them during the filling and seaming operations. Without this holding period, the cans are more prone to being damaged during these subsequent manufacturing steps.
As the line speeds of filling plants continue to increase through efforts to improve efficiency and productivity, the line speeds of container-making plants must also increase to meet the increased demand for containers. Accordingly, because of the reduced time available for the "green" (i.e., freshly made and still wet) tubes to set up and gain strength, it has become increasingly more difficult for parent tubes to go through secondary operations such as cutting the tubes to can lengths, flanging the cans, seaming end closures on the cans, etc., without being damaged.
In the case of composite containers for refrigerated dough products, the above-noted problems are exacerbated by the use of low-tack adhesive for affixing the exterior label layer to the paperboard body wall of the can. The low-tack adhesive is typically used in order to permit the label to be removed substantially in one piece so that baking instructions or the like that are printed on the label are not destroyed during opening of the can. In such dough cans, typically the paperboard body wall is spirally wound such that its edges form a helical butt joint that is easily opened to gain access to the dough product. The butt joint is held closed by the exterior label adhered to the paperboard body wall. Thus, the strength and integrity of the can is dependent largely on the strength of the label and the adherence of the label to the body wall. When a low-tack adhesive is used for affixing the label, the green strength of the can is still further reduced, relative to a can made with high-tack adhesive. Additionally, the burst strength of the can is compromised.